Plot summary
Dr. Jennifer Keller is diagnosed with a psychological ailment. However, little does the Atlantis expedition realize that she has been exposed to body-switching technology, similar to the one that SG-1 found in the SG-1 episode " Avalon " that does not require the subjects to be in close proximity. Meanwhile Keller's consciousness faces a desperate struggle for survival inside the body of a wanted fugitive woman named Neeva. Eventually the team finds the device and Ronon destroys it just as Keller is about to be killed by Neeva's associate. Neeva is then presumably killed by her former associate, but both disappear so her fate is unknown.
Credits
Adapted from Wikipedia contributors, Stargate Atlantis season 5. HTML formatting and reference markers removed.